1. Field of the Invention
The present invention relates to a medical guide apparatus for breathcoordinated puncturing of the body or a body cavity, with a puncturing instrument connected to an ultrasound applicator.
2. Description of the Prior Art
A medical guide apparatus of the above type is known from U.S. Pat. No. 5,647,373. The guide apparatus enables the puncturing of sites or lesions which are visible in the ultrasound image. An ultrasound applicator and a puncturing instrument are fastened in freely movable fashion to a movable vertical support by means of a rod assembly. The rod assembly has arms that are connected movably with one another via joints. Position sensors acquire the position of the ultrasound applicator and of the puncturing instrument. The ultrasound applicator emits signals identifying the puncture target area to a control computer, and the control computer sets the direction of a puncture path to the target area. During application, the physician places the applicator on the patient for the graphic representation of the target area, and also places the point of the puncture needle on the skin surface in the vicinity of the target area. The direction of the needle is then automatically set by the guide apparatus. The puncturing can then be controlled in real time by means of simultaneously produced ultrasound tomograms. With this guide apparatus, only lesions that can be sonographically represented can be punctured. This guide apparatus is not suitable for lesions that can be made visible only by means of magnetic resonance tomography or computed tomography.
A further guide apparatus is known from German OS 29 36 259, wherein an ultrasound applicator is described to which a guide aid for a puncture instrument is fastened laterally. The guide aid is oriented in such a way that the puncture path through a body part to be examined is located in the window of the ultrasound applicator.
Puncturing aids for CT-controlled puncturings are commercially available, for example from the company Partner-Diagnostica. As a rule, these puncturing aids include a mount, a running rail graduated in centimeters, and a carriage located thereon that can be stopped. The carriage is provided with an angular scale with a mount and a pivot mechanism on which a diode laser with cross-optics is attached. Using the mount, a fixed mounting is possible for standard computed tomography systems. After determination of the puncture point and of the angle of puncture, the corresponding angle is set on the angular scale and the carriage is displaced far enough so that the laser cross coincides. This puncturing aid makes it possible to angle the puncture needle in a manner corresponding to the tilt of the CT gantry. Further angular positioning can take place within the slice plane. With such a puncture aid, a CT-controlled puncturing can be conducted on organs that are not moving. The system cannot be used if the area of examination is displaced, such as by breathing.
A puncture aid for CT-controlled puncturings is also described in U.S. Pat. No. 5,053,042. A planar guide and measurement apparatus is used in order to guide a puncture or biopsy needle to a previously determined target area specified by angular and radius coordinates in tomograms that were produced with the aid of CT exposures of the patient. The apparatus is fashioned in such a way that it can surround the body of a patient positioned on a patient table. The guide apparatus itself glides on rails that are attached to the longitudinal sides of the patient table, so that it can be positioned at any point in the longitudinal direction of the patient.
If it is necessary to puncture a site or lesion visible only in a magnetic resonance tomogram (MRT) or computed tomogram (CT), then the following problems arise due to the breath displacement of the organ. The intervention planning and the intervention are not possible in the same breath position; as a rule, the patient is not able to reproduce the breath position during the intervention planning and the intervention; and external skin markers cannot be used with organs that are displaceable by breathing. This set of problems occurs in particular for liver sites which are visible only in the magnetic resonance tomogram, but the problem is also known from computed tomography, and in that context also concerns liver sites, which for this reason are punctured--if at all possible--under sonographic control. In addition, this problem occurs in computed tomography of the lungs, where, due to the high degree of breathing movement of the caudal lung segments, lung sites are known to be difficult to puncture, especially if they are smaller than 1 cm. In comparison to computed tomography, in magnetic resonance tomography, with a closed magnetic resonance tomography apparatus, there is also the particular problem that punctures can in principle take place only outside the magnetic resonance apparatus. In addition, many puncture apparatuses are not compatible with magnetic resonance apparatuses, and thus cannot be brought into the imaging volume of the magnetic resonance apparatus.